Efficient Luminescent Halide Quadruple‐Perovskite Nanocrystals via Trap‐Engineering for Highly Sensitive Photodetectors

Abstract

elements to replace lead due to the high toxicity. Lead-free halide perovskite NCs have recently received increasing attention for their low toxicity, high stability, and chemical diversity. [3-8] The most direct way is usually isovalent substitution of Pb 2+ with Sn 2+. [3] Unfortunately, lead-free CsSnX 3 (X = Cl, Br, and I) NCs is extremely unstable because of the easy oxidation of Sn 2+ into Sn 4+ in air. [3] Subsequently, A 3 M ' 2 X 9-type layer perovskite, A 2 MM ' X 6-type, and A 2 BX 6-type double perovskite (where A denotes alkali-metal ions; M, M' and B denotes monovalent-, trivalent-, and tetravalent-cations; X denotes halogen ions) with high stability have been reported. [9-20] However, optoelectronic devices based on these lead-free perovskite NCs have made limited progress. Such as, photodetectors based on lead-free perovskite NCs exhibited low responsivity (typically <1 A W −1). [17,18] This is mainly due to the low crystallinity, prominent charge-carrier trapping, and short charge-carrier lifetimes of these NCs. In this paper, we report, for the first time, the colloidal synthesis of a series of trigonal (R3̅ m) vacancy-ordered quadrupleperovskite NCs, i.e., Cs 4 CdSb 2 Cl 12 , Cs 4 MnSb 2 Cl 12 , Cs 4 CdBi 2 Cl 12 , and Cs 4 MnBi 2 Cl 12. The photoluminescence quantum yield (PLQY) can be enhanced by 96-fold while the PL lifetime can be enhanced by 77-fold in Cs 4 MnBi 2 Cl 12 NCs through metal alloying. Studies of the charge-carrier dynamics including temperature-dependent PL and femtosecond (fs) transient absorption (TA) measurements were performed to clarify the mechanism of the PL enhancement, which is due to the elimination of the charge-carrier trapping process and increased crystallinity. Besides, the PL-peak position can be tuned continuously from 590 to 640 nm by changing the MnCl bond distance via metal alloying. Finally, we fabricate photodetectors based on quadruple-perovskite NCs, which exhibit high responsivity (0.98 × 10 4 A W −1) and an EQE of 3 × 10 6 %. The responsivity is much higher than previous reported photodetectors base on lead-free perovskite NCs. These results show that quadruple-perovskite NCs open new possibilities for optoelectronic applications. The colloidal synthesis of halide quadruple-perovskite NCs was performed using a modified hot-injection method-for details see the Experimental Section. [14] As shown in Figure 1a,b, replacing M in A 2 MM'X 6 with one M'' (M'' denotes a +2 cation) The colloidal synthesis of a new type of lead-free halide quadruple-perovskite nanocrystals (NCs) is reported. The photoluminescence quantum yield and charge-carrier lifetime of quadruple-perovskite NCs can be enhanced by 96 and 77-fold, respectively, via metal alloying. Study of charge-carrier dynamics provide solid demonstrate that the PL enhancement is due to the elimination of ultrafast (1.4 ps) charge-carrier trapping processes in the alloyed NCs. Thanks to the high crystallinity, low trap-state density, and long carrier lifetime (193.4 μs), the alloyed quadruple-perovskite N...

2D Perovskite Single Crystals for Photodetectors: From Macro‐ to Microscale

“…Moreover, 2D lead-free perovskite crystals may be a new hotspot, as well as lead-free perovskite microcrystals, because of the effect of the toxic Pb(II) on humans and the environment. [112][113][114] We think 2D perovskite single crystals and their applications may be focused on the following aspects in the coming future. 1) Large-scale 2D perovskite single crystals.…”

Toward Green Optoelectronics: Environmental-Friendly Colloidal Quantum Dots Photodetectors

“…Compared to other optoelectronic devices based on perovskite materials, however, heavy metal-free PQDs and their PD applications have attracted less attention so far. This might be due to the difficulties in the synthesis of Pb-free PQDs as well as low device performance compared to Pb-free 2D/3D perovskite films, resulting from the low crystallinity, prominent charge-carrier trapping, and short charge-carrier lifetimes of these PQDs (Bai et al, 2021). In spite of this fact, it is still of importance to develop nontoxic and nonhazardous PQD-based PDs as they offer facile bandgap tunability and consequently good selectivity of response range.…”

“…Using the stable PQDs in an ambient condition, the author demonstrated the photocurrent gain (I Photo /I Dark ) up to 53 at the applied bias 5 V from Cs 3 Br 2 I 9 PQDs under the light illumination (solar simulator, 0.65 W/cm −2 ). Recently, Bai et al (2021) -1 , 4.5 × 10 10 Jones, and 2.9 × 10 5 %, respectively, under 365 nm wavelength light source.…”

Ultrasensitive Temperature Sensing Based on Ligand‐Free Alloyed CsPbClxBr3−x Perovskite Nanocrystals Confined in Hollow Mesoporous Silica with High Density of Halide Vacancies

“…[ 27–29 ] Recently, the advancements in scalable synthesis, [ 30 ] and post‐chemical treatment and surface engineering [ 31,32 ] have promoted the substantial progress of LHP NCs in sensing, [ 33–35 ] optoelectronics, [ 23,31,36 ] anti‐counterfeiting, [ 37,38 ] and more. [ 39,40 ] For temperature sensing, S r up to 7.12% (100 °C) and 10.04% (−130 °C) have been achieved with LHP NCs based materials. [ 6,41 ] Despite their great potentiality in high‐sensitivity temperature sensing, LHP NCs suffer from the poor stabilities against multiple external perturbations such as heat, light, and water.…”